My Solar Install - Fiberglass RV


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Old 03-15-2014, 02:01 PM   #1
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My Solar Install

I'll start by stating, my background is electrical engineering. I also served in the Air Force and believe in over-kill rather than be caught short.

I just finished designing and installing a solar system in my pickup camper. My goal was to generate enough power for full-time winter use without using tilting panels. I feel it will work for several days with overcast conditions. In winter I would be fighting low angles of solar incidence, limited sunshine, and higher energy demands. I considered tilting panels however many of these mechanisms cost nearly as much as buying additional panels. The projected increase with tilt was 30%. Adding two more panels would increase my energy input 50%...a better deal with the benefit of more power all the time. Tilting panels are a nuisance. They run the risk of forgetting to lower them and damaging from tree limbs.

I plan to boondock almost exclusively. So, reliable power is important to me. I will be living in my camper extensively during the next year as I complete a yacht restoration project. This extra power provides me all the comforts I need.

Physical Constraints: My battery compartment holds one 165 lb 225 A-H 8D gel cell battery. I have space in the generator compartment for one or two more if weight was not a factor. One is fine. Perhaps in the winter I might need another battery if I were in the cold north. My plan is to use the generator space to store an outdoor propane grill.

Battery: Gel cells are noted for their cycling longevity. If discharged to 70%, they can go 3000 cycles. That is over 8 years with daily cycling. At a 50% discharge, longevity drops to 1800-2000 cycles--5 years. I got this battery for $50 as a take out from a yacht and it had not seen much use. My plan is to use it up until it fails and then consider replacement options--probably replacing it with the same although I hope lithium techno guy prices drop in that time period. I am hoping for 3 years use with gentle loving care. It is a 2011 battery.

Solar Panels: I bought my four 105 watt mono crystalline solar panels (420 watts total) at Home Depot and used my 10% military discount. Cost was $132 per panel. The rule of thumb on yachts is to figure 5 hours at full power for a conservative daily power input. From experience with fixed panels this is a good estimator. For 5 hours that works out to 2100 watts or 175 A-H.

Optimization: Solar panels stop charging when the voltage drops below 12V. I arranged my four panels in an unobstructed area on my roof. I have two panels in series 36V nominal voltage, in parallel with another pair at the same voltage. This means my panels start charging earlier and keep charging until night fall as the voltage is typically well above 12V most of the time. If shaded this configuration would produce less power that four panels in parallel. I could have put the all in series for 72 Volts but the shading factor would be worse.

Charge Controller: I bought a Tracer 4210 40 Amp MPPT charge controller--a MOPT is a more efficient type of controller that conveys excess voltage into higher current levels at 12V and can be biased for three stage charging of gel cell batteries. So the maximum amount of energy is going into my battery. I am not sure I like this charge controller. I would considers different brand next time as the charging voltages seem a big high on float--just under 14 volts.

Shore Power Charging: I upgraded my converter to a modern multistage charger, mostly to condition the battery. I used it initially and now no longer use it. It was difficult getting the necessary information from the manufacturer but I did find one that had a jumper to drop the charging bias voltage by 0.4 Volts to meet the lower voltage requirements of a gel cell battery. My model, made by progressive dynamics is a 35 amp model. Note, they offer 35 Amp, 45 Amp, and 55 Amp chargers. Gel Cell batteries need slower charging so I chose the smallest model converter upgrade to save my gel cell from damage due to overcharging.

Inverter: I installed a Sunforce 11240 1000 watt pure sine wave inverter. I do not recommend it unless you are willing to modify it. I wired it such that it powers only the camper outlets, which are also powered through the shore power switch when that source is selected . I made it idiot proof because it was the smart thing to do. The AC outlet circuits energized will include TV, TiVo, Blu-ray player, Mac Mini, Apple Airport Extreme WiFi, Netgear switch, and a few other loads. My 1250 watt microwave requires more power than my inverter will deliver. If I can bond the inverter outputs together, that supply 500 Watts each, I can buy a smaller 1000 watt microwave that could be energized by the inverter. Larger inverters are heavier and draw more power. I wanted to size my inverter to match the loads.

I also bought a cheap model inverter, with plastic sides, thumb screw DC terminals and no way to permanently mount it. I modified it by removing the fake plastic heat sinks on the sides and replaced these with sheet metals sides with mounting flanges. I replaced the thumb screws with 8mmx125 nuts. That's how I made a $180 Chinese inverter work for me. If it cramps out I'll get a bigger one and upgrading its associated DC wire. I may pull it out and open it up to bond the two 500 watt outputs into one--of that is possible so that I can run a microwave.

Results: Since installing the solar panels I'm finding the big surplus of power is working well. I have seen 1-2 amps of charging when heavily obscured by clouds. This is plenty when I don't use the furnace. I used 50 A-H's last night running the furnace about 30% duty cycle (low was 20 degrees F rising to 50 degrees F now), which draws 3.6 Amps, the inverter, and parasitic loads.

My only regret is that I didn't choose a grid-tie inverter that could be hooked up at home to reduce energy costs. These are much more expensive. With a grid tie I could use my excess power to offset my electric bill.

Connectors: I used MC4 solar power connectors (highly recommended). I used heavily insulated 10 gauge conductors, and 5/16" marine cable glands to bring the wire into the camper. I also used MC4 junction terminators to join the wires on the roof, securing these to the solar panels with extra long 3/16 inch pop rivets. I highly recommend these solar power connectors; they work great, are easily serviced or expanded. If I choose to add more panels it will be very easy to do.

A few numbers: At 9:30 this morning here at latitude 41 N. I was putting 10 amps into my battery which were at about 76%. At noon here now it is putting in over 16.7 Amps. I am down 25.2 A-H on a total capacity of 225 A-H. 87% charge here at noon. At 12:30 I am at 90% and current varies with the cloud cover. 92.8% at 1 PM. It shows fully charged at 2:40, but I'm sure it is still a few percent below fully charged, however for practical purposes, it works great. I have high confidence it will work in more cloudy conditions as long as my used battery holds out.

So what does it all mean?

Excess solar capacity is always good.

Excess battery capacity means your % discharge is less and battery life goes way up.

The penalty for more battery weight is not worth it, as it is easy to replace a battery that to carry it around for long periods. I could add another battery but do not need it unless I was seeing more than three days of overcast conditions in wintertime. A second battery would give me 5 days reserve at 50% discharge--that is huge. I could then go a week at 75% discharge and two sunny days would top me off again.

I would choose greater battery capacity for difficult winter conditions--far northern Canada in the winter, if my loads were higher, for mission critical applications, or for fixed location use.

Could I have gotten by with fewer solar panels? Yes, for not much cost savings at the expense of worry about my system.

Charging voltages parameters vary by the manufacturer. Gel cells are fussy on these, but best suited to solar charging in my opinion. I decided not to worry about by battery too much. Time will tell on this. AGM or flooded batteries are not so worrisome but don't last as long. For shore charger only use, without solar panels, I would choose AGM and a bigger, faster charger, or flooded batteries if I was willing to deal with the maintenance.
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Old 03-15-2014, 03:15 PM   #2
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Connectors: I used MC4 solar power connectors (highly recommended). I used heavily insulated 10 gauge conductors, and 5/16" marine cable glands to bring the wire into the camper. I also used MC4 junction terminators to join the wires on the roof, securing these to the solar panels with extra long 3/16 inch pop rivets. I highly recommend these solar power connectors; they work great, are easily serviced or expanded. If I choose to add more panels it will be very easy to do.
I have the MC4 Connectors as well. Although my panels are not mounted to the trailer my controller is. A simple clicking together of the MC4 connector from the panel to the controller connection has my portable panel up and running.

Thanks for taking the time to share your decisions as to what to go with. Very helpful to those of us looking to upgrade our older systems in the not to distant further.
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Old 03-15-2014, 03:40 PM   #3
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I was interested in the Tracer solar controller. I went to their website and read the specifications of the different stages and charge levels. I was particularly looking at what their equalization charge level was, I see it is at 14.8 volts. That is a good level. When I read a little further I realized that you had the gel batteries, I noticed there is no equalization level shown for a gel battery. I am not that familiar with gel battery, is there a reason why the specs would not show an equalization level for gel?

It sure appears to me you have a good design. I did not see mention of fusing and a kill switch, I would like to hear how you handled these.
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Old 03-15-2014, 03:51 PM   #4
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Good post with lots of info. Thanks
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Old 03-15-2014, 07:38 PM   #5
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Mr. Sailor, my thanks as well for all the data. Splitting the difference between parallel (more shade tolerant) and series (more efficiency with MPPT controller) seems like a good idea.

You have a basic problem with your plan though, 41 N latitude is way too far north!
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Old 03-15-2014, 07:43 PM   #6
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You have a basic problem with your plan though, 41 N latitude is way too far north!
Some of the most beautiful places to camp can be found at 41 N latitude and further up... would be a shame to own a trailer set up and a solar system that didn't work in such areas.
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Old 03-16-2014, 12:16 AM   #7
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Quote:
Originally Posted by Paul Braun View Post
I was interested in the Tracer solar controller. I went to their website and read the specifications of the different stages and charge levels. I was particularly looking at what their equalization charge level was, I see it is at 14.8 volts. That is a good level. When I read a little further I realized that you had the gel batteries, I noticed there is no equalization level shown for a gel battery. I am not that familiar with gel battery, is there a reason why the specs would not show an equalization level for gel?



It sure appears to me you have a good design. I did not see mention of fusing and a kill switch, I would like to hear how you handled these.


I have a fuse on the solar. 30 Amp. I may down grade it to a 25 in the future. I also have a DC disconnect between the battery and converter. Switches off and all DC loads are disconnected bit not the solar charging which requires the fuse to be pulled to disconnect. Inverter has internal breaker and on off switch. I am not sure what parasitic loads are present when this is off.

For more info on the pluses and minuses of the solar charge controller and inverter, read my reviews on Amazon.
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Old 03-16-2014, 12:20 AM   #8
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Originally Posted by MCDenny View Post
Mr. Sailor, my thanks as well for all the data. Splitting the difference between parallel (more shade tolerant) and series (more efficiency with MPPT controller) seems like a good idea.

You have a basic problem with your plan though, 41 N latitude is way too far north!

I agree. I prefer the Caribbean. My reasons for buying this camper rather than fixing up my other one are to have more time for boat work (instead of commuting) so I can finish it spend next winter in Bermuda.
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Old 03-16-2014, 12:21 AM   #9
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Originally Posted by Carol H View Post
Some of the most beautiful places to camp can be found at 41 N latitude and further up... would be a shame to own a trailer set up and a solar system that didn't work in such areas.

You are right about that. I love Ontario's cottage country and heading north in the summer. I plan to spend time exploring Canada every summer from now on.
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Old 03-16-2014, 06:34 AM   #10
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Some of the most beautiful places to camp can be found at 41 N latitude and further up... would be a shame to own a trailer set up and a solar system that didn't work in such areas.

Geez Carol, I was kidding him. I live at 41N.
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Old 03-16-2014, 09:56 AM   #11
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Shows the solar panel mounting and junctions and cardboard placed over the solar panels to avoid energizing and sparking.

You can see the shiny new sheet metal sides custom made with mounting flanges for inverter. I tossed out the phony plastic heat sink sides. I'd read reports of interference from this device and wanted to fully enclose it in metal as it should have been built.

The Tracer Solar charge controller had crappy screw terminations to bond the wire. I had to solder the wire ends to protect the from crushing the wire ends when tightening these. If I had square ferrules to crimp on the ends to strengthen them, that would have been the best solution. I only had small gauge ferrules. There is an RJ45 connector to the the remote display. I found the display hard to read. I plan to build a new longer cable out of Cat-5 and place it higher up where I can read it easier. This display is polarized and difficult to read unless directly in front of you. It also attracts dust and wiping it off, turns the display into a mess impossible to read. Once I relocate it I'll try to spray it with something to remove the static that attracts the dust.
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Old 03-16-2014, 07:28 PM   #12
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I just realized the solar panel output was much greater than listed, I was actually getting over 20 amps of charging current, the reading was less because I had 4-5 amps of loads running at the same time. I have about an amp or two in parasitic loads, plus 3.6 amps intermittently with the furnace and brief heavy loads of 7.5 amps on the water pump.
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Old 03-20-2014, 10:34 AM   #13
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Skip to bottom for solar panel production numbers:

I have been analyzing my solar power production by shutting off my furnace, inverter, and then hitting the kill switch for all DC loads, in the morning after letting my pup out for peeps and poops (the adult doggie can hold it forever). There is enough residual heat here to keep me warm for a while as I crawl back into bed to snooze a bit more, or read for a while.

As I stated earlier, I am at 41 deg North, and today we are just after the spring equinox. So that means the days are about the same length as the nights. 12 hours.

One item I installed that I use frequently is a LinkPro battery monitor. I programmed it with the estimated Amp Hour Capacity of the battery I am using. New capacity is 225 amp hours. I guess the capacity to be 220 amp hours, but short of depleting it completely, I don't know the true capacity of this battery. It is probably less than this amount.

My battery is a 165lb gel cell 8D size that a good friend in the marine industry took out of a yacht he was servicing. The owner wanted three new batteries and this one serviced the anchor windlass and was not used much. It is a 2011 model. I had difficulty charging this because the sensitive nature of gel cells. I finally gave in and bought a 35 A charger and the company sent me a jumper to drop the bias voltage by .4A to support gel cell charging. After installing this, I left it charging for 4-5 days to try to recover to the maximum amount of charge it would take.

About this point I installed my solar panels which I've been using for about a week. During the last five days I've been collecting data to determine my rate of recovery for my battery. On the second day I accidentally put the fridge on AC electric which draws a whopping 28 Amp through my inverter. I caught it when the LinkPro low battery alarm I'd set went on. That evening I decided to use my normal loads for the inverter and furnace and by morning I was down over 90 amp hours. The following day was overcast and it took an extra day to fully recharge.

At this point I decided to see what my normal night-time loads were, how many amp-hours I could expect to recover in various conditions, and consider how to use surplus power.

I discovered that with my panels mounted flat, and not tilted, I could expect to generate as much power in the first 3.5 hours, and the last 3.5 hours as a typical hour between 10:30am and 3:30pm. Call it 7 hours of charging at this rate. The true amount would be greater than this....this seems to be a good rule of thumb.

My 105 watt panels each produced
Overcast days: 15.75 amp hours
Partly Cloudy: 25 amp hours (estimate as the batteries would top off about 3pm)
Clear days: a 32 amp hours (estimate as the batteries would top off about 2pm)
Theoretical maximum charging capability is 43.75 amp hours.

So I have enough power to fully recharge my batteries if I am careful on my energy consumption on an overcast day. I have no difficulty charging on a sunny day.

I considered what I could do with two more panels:
1) This would allow me to fully recharge on an overcast day.
2) This would provide a modest amount of charging on a dark and stormy day.
3) This would allow me to go several days in dark and stormy conditions.
4) On a bright day I could:
a) Operate my refrigerator on AC during the day to reduce my propane usage or,
b) Discharge my batteries deeper operating an electric blanket at night and still top off the batteries the next day.

My conclusion is the more solar panels you have, the more options you have.

A final thought. Lithium-Ion batteries are still unaffordable. However, these provide nearly three times the power for 1/2 the weight. in 5-10 years, everyone will be using lithium batteries which will last longer, discharge deeper, charge faster, and won't need solar charge controllers.
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Old 03-20-2014, 11:29 AM   #14
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Conrad, Great report with all your detailed data. I for one was very interested in your panel output, I'm probably going with the same panel as it fits the space well that I'm going to put one. Thanks for the info.
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